hoagland



Jan. 31, 1956 K, HOAGLAND 2,733,365

ION TRAP ELECTRON GUN FOR CATHODE RAY TUBES Filed oct. 1. 1951 Fig.

INVENTOR. KENNETH A. HOAGLAND A TTORNEYS Unite Sttes Patent Ofifice 2,733,365 Patented Jan. 31 1956 ION TRAP ELECTRON GUN FoR CATHODE RAY TUBES Kenneth A. Hoagland, Newark, N. J., asslgnor to Allen B. Du Mont Laboratories, Inc., Clifton, N. J., a corporation of Delaware Application October 1, 1951,'Serial No. 249,120 14 Claims. (Cl. 313-82) The present invention relates to cathode ray tubes and more'particularly to improvements in cathode ray tube ion trapping devices of the type disclosed in U. S. vPatent 2,637,828, issued May 5, 1953, assigned to the assignee of the present invention.

In the device disclosed in that application, the ion trapping anode is in the form of a tubular member having While the Accordingly, it is an object of the present invention to provide an improved ion trapping electron gun for cathode ray tubes.

It is a further object of this invention to provide an scribed in my above referred to application.

The electron gun comprises a cathode-grid assembly 6, a second grid 8 and an accelerating anode-focussing electrode assembly 10 secured together in "spaced relationship ia'long the-longitudinal axis of fth'ene'ck 2.

As shown in Fig. 2, the cathode grid assembly 6 includes 'a tubularcathode member lit-supported 'coa'xially within a thimble-shaped grid member 12 having a coaxially aligned aperture 1d "by an insulating disc -16. A suitable electron emissive material :18 formedonthe "end 10, provides asource of electrons for the'cathode ray tube.

The second grid 8, as illustrated in Fig. 2 is a cupshaped member having-an axially aligned aperture 21 and an outwardly extending rolled flange 22 provided with diametrically disposed ears 24, see Fig. :1. Theiaccelerab ing anode focussing assembly it which forms .the remaining unit of the electron ;gun assembly comprises a preaccelerating anode 26, a-focussing electrode 28 and 2 an accelerating anode 30. the preaccelerating anode is formed of a tubular metal to the central axis of the member and perpendicular to the axis of alignment of the cathode-grid assembly 6 and grid 8. The accelerating anode 30 is likewise a tu- In assembling the electron gun to provide means for trapping undesirable ions, Strap 46 issecured'to the outer cylindrical surface of the preaccelerating anode 26 as shown.

adapted to receive rods 50 of insulating material. The axes of the tubular end portions 48 are inclined to the central axis of anode 26, focussing electrode 28, and anode 3t and areperpendicular to the planeof the aperture 34 in the reduced end portion 32 of anode 2 With the rods 50 disposed in the mannerdescribed, the

of passing the rodsthrough apertures, not shown, in the The grid 8 is thereafter -secured 1n position by means of tubular members 52 which are likewise passed over the rods and secured to the cars 24 tubular portions are clinched on the rods. In assembling the grid S'and cathode grid assembly 6 with the accelerating anode-focussing electrode assembly 10, the grid 3 and cathode-grid assembly 6 are spaced along a common axis with the grid 8 in juxtaposition to the reduced end of the preaccelerating anode 26. In providing such an an alignment, the common axis of the cathode-grid assembly 6 and the grid 8 is perpendicular to a plane which passes through the aperture34 in the reduced or spherical end portion 32.

With the electron gun structure assembled in the neck of the tube, the cathode-grid end of the electron gun structure is supported in the neck of the tube by lead wires 55 connected through the base 4 to prong type terminals 57.

Referring now to Fig. 3, there is illustrated another form of preaccelerating anode embodying my invention in which an aperture 58 is formed in the spherical end portion 60 of a cylindrical cap 62; the cap being received and secured on the end of a tubular member 64.

In operation, electrons are released from the electron emissive material 18 and are constricted into a bundle in passing through the apertures 14 and 21 respectively. Thereafter, they are accelerated along the common axis of the cathode-grid assembly 6 and grid 8 through the aperture 34 of the preaccelerating anode 26 and into the space defined by the preaccelerating anode. Within the preaccelerating anode 26, any ions which are released at the cathode and carried along in the stream of electrons are separated from the electrons in a manner such as described in my first application mentioned hereinabove. The electrons are then focussed by the action of the focussing electrode 28 and are finally accelerated toward the screen of the cathode ray tube by the accelerating anode 30. In this connection, it will be understood that while I have described my invention in connection with an electrostatically focussed electrode such as described in the later of my abovementioned applications, it will be equally as useful in electron gun structures in which focussing of the electrons is obtained by electromagnetic means.

In an electron gun structure such as I have hereinabove described, the preaccelerating anode 26 permits an axial dimensional reduction of the tube as well as a reduction of the diameter of the neck thereof. The anode 26 with the reduced or spherical end portion and the aperture therein permits the spacing of the second grid adjacent thereto without an intermediate bent or axially incined tubular portion as has been the practice heretofore in the so-called bent gun structural types. Further, an ion trapping anode structure such as I have hereinbefore described lends itself to simple, inexpensive, fabricating process and, because of its spherical end portion, eliminates the need of additional parts such as rolls in the anode structure or corona rings which are necessary to prevent excessive breakdown or stray emission from the lower potential electrodes of the assembly. Still further, an ion trapping anode such as I have described hereinabove in connection with an electron gun assembly provides a symmetrical electrostatic field about the common axis of the cathode-grid assembly wherein lack of symmetry between the adjacent grid and anode would result in undesirable distortion of the electron beam.

While I have described preferred forms of my invention, it will be apparent that other forms may be used, all of which are intended to come within the scope of the claims which follow.

What I claim as new and desire to obtain by Letters Patent of the United States is:

1. In a cathode ray tube, a cathode and a grid aligned on a common axis and an anode aligned on a second axis inclined to said common axis, said anode having a spherical end portion with an aperture therein facing said cathode and grid, said aperture being formed in a plane perpendicular to said common axis said second axis passing through said end portion.

2. In a cathode ray tube, a cathode and grid aligned on a common axis and an anode aligned on a second axis inclined to said common axis, said anode having a spherical end portion adjacent said grid and an aperture formed in said spherical end portion in a plane perpendicular to said common axis said second axis passing through said end portion.

3. In an electron gun, a cathode and a grid aligned on a common axis, an anode aligned on a second axis inclined to said common axis, said anode having a spherical end portion with an aperture therein, said aperture being in a plane perpendicular to said common axis said axis passing through said end portion.

4. An anode for electron guns, said anode comprising a straight tubular portion having a spherical end portion with an aperture therein aligned in a plane inclined to the axis of said tubular portion.

5. In a cathode ray tube, a cathode, a first grid and a second grid aligned on a common axis and a preaccelerating electrode, a focussing electrode and an accelerating electrode aligned in spaced relationship on a second common axis inclined to said first-mentioned common axis, said preaccelerating anode having a spherical end portion facing said second grid, said end portion having an aperture therein formed in a plane perpendicular to said first-mentioned common axis said second common axis intersecting said end portion.

6. In a cathode ray tube having a grid and a straight tubular accelerating anode in juxtaposition with the axes of said grid and anode inclined to each other, said anode having a reduced end portion and an aperture therein, said aperture being formed in a plane perpendicular to the axis of said grid and at an acute angle to the axis of said tubular anode.

7. An anode for electron guns, said anode comprising a straight tubular portion having a hemispherical reduced end portion with an aperture therein aligned in a plane inclined to the longitudinal axis of said tubular portion.

8. In an electron gun having a grid and an accelerating anode in juxtaposition with the axes of proximal parts said grid and anode inclined to each other, said anode having a reduced end portion with an aperture therein, said aperture being formed in a plane perpendicular to the axis of said grid.

9. An anode for electron guns, said anode comprising a straight tubular portion and a cap secured to the end thereof, said cap having a hemispherical reduced end portion with an aperture therein aligned in a plane inclined to the longitudinal axis of said tubular portion.

10. In a cathode ray tube, a cathode and a grid aligned on substantially a common axis and an anode aligned on an axis inclined to said common axis, said anode comprising a straight tubular member having a reduced end portion completely contained within the axial projection of the wall of said tubular member, said end portion having an aperture therein of less cross-sectional area than the cross-sectional area of said tubular member and with the reduced end portion edge surrounding said aperture substantially in a plane which is inclined to the longitudinal axis of said tubular member and substantially normal to said common axis.

11. In a cathode ray tube, a cathode and a grid aligned on substantially a common axis and an anode aligned on an axis inclined to said common axis, said anode comprising a straight tubular member having a substantially spherical end portion completely contained within the axial projection of the wall of said tubular member, said end portion having an aperture therein of less crosssectional area than the cross-sectional area of said tubular member with the central axis of said aperture inclined to the longitudinal axis of said tubular member and substantially in alignment with said common axis.

12. In a cathode ray tube, a cathode and grid aligned on substantially a common axis and an anode aligned on an axis inclined to said common axis, said anode comprising a straight tubular member having a substantially spherical end portion completely contained within the axial projection of the wall of said tubular member, said end portion having a circular aperture therein of less cross-Sectional area than the cross-secti0nal area of said tubular member with the edge of said end portion defining said aperture in a plane inclined to the longitudinal axis of said tubular member and normal to said common axis.

13. In a cathode ray tube, an electrode comprising a straight tubular member having a hemispherical reduced end portion completely contained within the axial projection of the wall of said tubular member, said end portion having an aperture therein of less cross-sectional area than the cross-sectional area of said tubular member with the edge of the reduced portion defining said aperture being substantially in a plane inclined to the axis of said tubular portion.

14. An electrode for cathode ray tube electron guns 2'211'613 comprising a straight tubular member having a hemi- 6 32581149 spherical reduced end portion completely contained withm the axial pIOJflCtlOIl of the wall of said tubular member, 2472766 said end portion having an aperture therein of less crossg' gg g sectional area than the cross-sectional area of said tubular {2 member with the edge of the reduced portion defining said 10 5 6 aperture being substantially in a plane inclined to the axis 2644906 of said tubular portion.

References Cited in the file of this patent UNITED STATES PATENTS Bowie Aug. 13, 1940 Schutze Oct. 7, 1941 Parker Dec. 30, 1941 Woodbrldge June 7, 1949 Kelar Jan. 31, 1950 Hoagland et a1 July 31, 1951 Szegho Oct. 30, 1951 Phillips et al May 13, 1952 Bondley July 7, 1953 

